This invention relates to an ion exchange resin insolubilized as to organic components from the resin, a process for preparing the resin and an apparatus for producing ultra-pure water by the resin.
In the semi-conductor industry, the market for LSI (large scale integrated circuit) has been rapidly expanded, and LSI having a higher degree of integration of up to 64K bits is now in the mass production, and attempts to produce LSI on the integration level of 256K bits are now going on and research for LSI on the integration level of 1 M bits, that is, ultra LSI of the next generation is under way. With the progress in LSI-zation, the minimum pattern dimension can be reduced, for example, the minimum pattern dimension of LSI will be 2-3 .mu.m, and that on the integration level of 1M bits, i.e. VLSI, will be less than 1.5 .mu.m.
Pure water is used in various washing steps in the process for producing LSI to remove chemicals and fine particles remaining on the wafer surfaces after acid treatment or organic chemical treatment of wafers. Thus, (1) ions, (2) fine particles, (3) microorganisms, (4) organic matters, etc., if contained in the pure water, will have an adverse effect on the oxide film, polycrystalline film, wiring, etc. to be incorporated into the wafers, impairing the electric characteristics and reliability of LSI. The adverse effect will be more serious with increasing integration level, and the requirements for pure water quality will be more stringent. Needless to say, the pure water quality available from the current apparatus for producing pure water cannot meet the requirements for semi-conductors on the integration level of 1-4 M bits.
Furthermore, pure water is required in the medical field, for example, as injection liquid, and also in the nuclear energy field. The adverse effects by typical ones of said adverse factors (1) to (4) on the products in the relevant fields including these medical and nuclear energy fields are summarized in the following Table.
TABLE __________________________________________________________________________ Field Phenomena Problems Adverse effects on products __________________________________________________________________________ ##STR1## ##STR2## ##STR3## ##STR4## __________________________________________________________________________
That is, organic matters react with oxygen in the presence of microorganisms to propagate the microorganisms. As a result, the microorganisms are discharged as an effluent in the semi-conductor field, lowering the wafer purity. The maximum particle size must be desirably less than 1/5 of the minimum pattern to prevent occurrence of short circuit. Since the average size of microorganisms is about 1 .mu.m, the micoroorganisms themselves are a problem even on the integration level of 64K bits. As to the organic matters themselves, though present in a very small amount, the specific substances contained in the organic matters, for example, Cu, Fe, P, etc. are required to be less than 1 ppb.
In the medical field, the microorganisms produce metabolic products through reaction, thus increasing pyrogens. Consequently, the product purity is lowered and the pyrogenic trouble is brought about. In the nuclear energy field, the organic matters are converted to smaller molecules while forming COOH.sup.- and successively Co complexes, and the capacity for removal of radioactive wastes by ion exchange is lowered. That is, the radioactivity in the nuclear plant facility is increased.
From the foregoing, it can be seen that removal of organic matters from pure water can also reduce the adverse effects by other factors. A permissible concentration of organic matters in pure water for use in the production of semi-conductors on the integration level of 64K bits is now less than 300 ppb in terms of TOC (total organic carbon), whereas the concentration for the integration level of 1 M bits is as stringent as 50 ppb, and thus dissolution of organic matters from ion exchange resin or organic materials of construction used in an apparatus for producing pure water is a problem, which seems to be one of reasons why the current pure water production technique does not meet the requirements for VLSI. Organic matters are present even in the pure water produced according to the process for producing pure water for the integration level of 64K bits even after the multi-stage treatment by means of membrane separators and desalters as the major units, where dissolution of organic matters from the organic materials such as membranes or ion exchange resin used in the major units has been pointed out as a cause for their presence. The desalting treatment using ion exchange resin indispensable for the pure water production has also a problem of discharging of fine ruptured fractions of the resin particles generated by mutual collision of the resin particles or collision of resin particles with the apparatus walls, etc. from the mass of resin particles. Not in the apparatus for producing pure water, but in an apparatus for treating waste water, it is known to regenerate a synthetic adsorbent having ions as adsorbed on the surface by removing the adsorbed ions therefrom by dissolution in a liquefied gas (for example, U.S. Pat. No. 4,061,566). However, said U.S. patent nowhere shows that ion exchange resin is prepared by removing projections from the ion exchange resin.